JP5283134B2 - Control device adaptable to touch screen frequency - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for adapting the frequency of a touchscreen control device to adapt the touchscreen control device to a special operation characteristic of a specific touchscreen. <P>SOLUTION: The touchscreen system includes: a substrate which can propagate sound waves; at least one transmitting transducer which transmits a sound wave of a first burst length corresponding to an input signal; a reflection array which forms a sound wave of a second burst length by extending the sound wave of the first burst length; a receiving transducer which receives the sound wave of the second burst length; and an adaptable controller. The adaptable controller includes a reference oscillator which generates a first frequency; a microprocessor connected to the reference oscillator; a digital burst circuit; and a memory including a set of frequency correction values. The microprocessor outputs a burst control signal to the digital burst circuit. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates generally to touch screens, and more particularly to a method and apparatus for adapting the frequency of a controller to adapt the controller of the touch screen to the particular operating characteristics of a particular touch screen.

  Touch screens are incorporated into various types of displays, including cathode ray tubes (ie, CRTs) and liquid crystal display screens (ie, LCD screens) as information input means to the data processing system. If the touch screen is placed above or integrated with the display, the user can select the displayed icon or element by touching the position corresponding to the desired icon or element. . Touch screens are commonly used in a variety of applications such as POS systems, information centers, cash dispensers (ie, ATMs), and data entry systems.

  In certain types of touch screens, such as acoustic screens, sound waves or ultrasonic waves are generated using, for example, surface acoustic wave phenomena such as Rayleigh waves, Love waves or other sound waves, and directivity on the surface of the touch screen. Propagate well. In general, a single transmitting transducer, a single receiving transducer, and a pair of reflective arrays are provided on each axis of the touch panel. The transmit and receive transducers are connected to a controller, which generates drive signals that are supplied to the transmit transducers, amplifies, adjusts, and responds to signals from the receive transducers. The sound wave generated by each transmission transducer is reflected by a reflection array arranged near the periphery of the touch screen. The reflective array reflects sound waves at right angles throughout its length, producing a surface acoustic wave pattern that propagates to the active area of the touch screen. Propagating surface acoustic waves have a substantially straight wavefront with uniform amplitude. Opposing reflective arrays reflect propagating surface acoustic waves toward the receiving transducer. By monitoring the propagation time and amplitude of the surface acoustic wave propagating along each axis of the touch screen, the position of the wave attenuation point on the surface of the touch screen can be identified. This attenuation is caused by a finger, stylus or other object touching the screen.

  Typically, touch screen system manufacturers produce or purchase controllers that have a predetermined vibration frequency that is within a well-defined frequency range and whose reference frequency is provided using a crystal oscillator. In the manufacturing process, the characteristic frequency of each touch screen is specified, and if necessary, the characteristic frequency is adjusted so that the characteristic frequency of the touch screen and the oscillation frequency of the controller are sufficiently adapted.

  The characteristic frequency of the touch screen needs to be identified more carefully. The type of acoustic touch screen of interest here has the characteristics of a narrowband filter. The center frequency of the narrow band is determined by the interval between the reflecting elements and the velocity of the sound wave. When a short time burst is applied to the transmitting transducer, a series of long-lasting wave trains are detected after a delay time corresponding to the time for the sound waves to propagate to the receiving transducer at the shortest distance. The frequency spectrum of the incoming burst is usually very wide due to the short duration of the burst, but the spectrum of the output wave train is very narrow and has a sharp peak at a specific frequency Ideally. This particular frequency is called the characteristic frequency of the touch screen. The operating frequency of the touch system is required to adapt to the characteristic frequency of the touch screen.

  In principle, a touch screen ideally has a single characteristic frequency. However, due to manufacturing variations, the characteristic frequency may be plural or have a certain range. In the actual manufacturing process of a touch screen, there is substantially only one characteristic frequency of the touch screen, and costs and effort are invested to adapt to the oscillation frequency determined by the reference oscillator of the controller. In order to achieve the expected results in the manufacturing process of the touch screen, it is necessary to perform precise layout design of the array, strict control of the supply process of the raw materials to be obtained, and proper electrical testing of the reflective array. In addition, if there are unexpected changes or fluctuations, they need to be corrected immediately. For example, it may be necessary to redesign the array or create a new print mask. The adjustment, control and testing necessary to maintain the touchscreen's characteristic frequency properly has resulted in increased manufacturing costs and a factory with skilled workers in the difficulty of manufacturing acoustic touchscreens. However, the production yield will be reduced. This is an important solution in the current acoustic touch screen industry.

  In general, frequency maladaptation can be classified as essentially whole or partial. If frequency maladaptation is global, the cause of maladjustment affects the entire touch screen. For example, if the vibration of the reference oscillator of the controller drifts or fluctuates (for example, because the glass substrate is manufactured by a different glass manufacturer), the controller's oscillation frequency is reduced throughout the touch screen if the glass substrate has an unexpected sound speed. It can be adapted to a specific frequency of the touch screen. On the other hand, if the frequency maladaptation is partial, then maladaptation with the controller occurs only in certain areas of the touch screen.

  Overall and partial frequency maladaptation can result from a variety of causes. Although some causes of maladjustment can be eliminated by thorough quality control, the cost of such quality control can often be very high. For example, due to variations in the glass substrate of the touch screen, the sound speed fluctuates and overall frequency maladaptation occurs. It is economically impossible to control the glass supplier and control the manufacturing process so that the speed of sound of all substrates is within a predetermined narrow range. If the acoustic reflector array is printed directly on the cathode ray tube (CRT) faceplate, it becomes more difficult to manage the glass supplier and the manufacturing process. It is difficult to manage specific glass properties including glass chemical composition and thermal history (such as annealing time and annealing temperature) to eliminate overall frequency mismatch.

  Another cause of frequency maladaptation is variations in the reflective array printed on the substrate of the touch screen. This variation is caused, for example, by the deformation of the array mask during the screen printing process. Print mask deformation is particularly problematic when the array is printed directly on the CRT faceplate. Other array printing techniques, such as pad printing, are subject to alignment errors that occur during the printing process and cause further frequency maladaptation. Another cause of frequency maladaptation is due to improper calibration of the spherical geometric effects of the uneven substrate surface.

  There is a need in the art for a method and apparatus that adapts the oscillation frequency of a controller to the operating frequency of a particular touch screen. The present invention provides such a method and apparatus.

  The present invention provides a method and apparatus for adapting the frequency of a controller to the operating frequency requirements of a particular touch screen substrate that includes a reflective array. In particular, the controller according to the present invention outputs a burst signal to the touch screen transmit transducer or adjusts the signal from the touch screen receive transducer to accommodate a specific operating frequency characteristic of the touch screen substrate. Configured.

  According to one aspect of the invention, first one or more characteristic frequencies of a particular touch screen are identified. The frequency of the controller used with this board is then adjusted to accommodate one or more measured characteristic frequencies of the board, and the two components are paired as an adapted set (coupling). Or pairing). According to another aspect, the substrate and controller are coupled before adapting the operating frequencies of the two components (touch screen substrate and controller). After coupling, the system is initialized during which the frequency characteristics of the touch screen substrate are identified. Thereafter, the characteristic frequency of the controller is adjusted to adapt to the frequency characteristic of the substrate. The system may periodically retest the board's characteristic frequency and readjust the controller output as necessary.

  In one embodiment of the present invention, an adaptive controller according to the present invention employs analog signal processing techniques and a crystal reference oscillator, primarily when trying to eliminate errors due to overall frequency maladaptation. A digital multiplier is used to process (transform) the output of the reference oscillator to generate a tone burst having the desired frequency that is transmitted to the transmitting transducer and / or to generate a baseband signal that is converted to the frequency used by the receiving circuit. To do. The burst length is determined by a burst circuit. The desired operating frequency is determined by a built-in mixer circuit that compares the output signal of the digital multiplier with the appropriately adjusted output signal of the receiving transducer. Then, a desired operating frequency is determined using the output signal from the mixer built-in circuit.

  In another embodiment of the present invention, the adaptive controller according to the present invention uses digital signal processing techniques and a reference crystal oscillator to calibrate overall and partial frequency variations. In this embodiment, the digital signal processor receives the digitized and filtered output from a pair of mixers. The input signals to these mixers are a pair of reference signals, one of which is a receive transducer RF signal that is phase shifted by 90 degrees, appropriately filtered, and amplified. This embodiment is an example of use of a phase sensitive controller in which a set of mathematical contents such as the phase and amplitude of a received signal is digitized. When the digitized set of information can be processed by a digital signal processor algorithm, a software adjustable frequency filter can be applied to the received signal. Based on the correction value stored in the memory, the digital signal processor adapts the frequency filter to a specific center frequency that preferably varies depending on the delay time after the last burst is transmitted. That is, the system can adapt to variations caused by partial variations in the acoustic reflection array.

  According to yet another embodiment of the present invention, a non-crystal local oscillator can be used to obtain a reference signal in an adaptable controller. By using such an oscillator, the controller can be sufficiently miniaturized and mounted directly on the substrate of the touch screen. Also, the feedback loop can be used to compensate for oscillator drift. In this embodiment, the conditioned RF signal from the receiving transducer of the touch screen is mixed with the output signal of the local oscillator. The IF (intermediate frequency) output signal from the mixer is sent to a discrimination circuit that generates a voltage, the sign of which depends on whether the frequency is higher or lower than the desired frequency, and its amplitude is offset from the desired frequency It depends on the degree of (deviation). The output signal from the discriminator is used to adjust the local oscillator frequency to match the touch screen frequency. In order to achieve the desired burst frequency, the stable output signal from the local oscillator is mixed with the output from the intermediate frequency oscillator.

  In yet another embodiment of the invention, the burst is sufficiently wide enough to use a voltage-controlled variable frequency band filter to sufficiently adjust only the center frequency of the circuit processing the receiving circuit.

  A more detailed understanding of the nature and advantages of the present invention may be gained with reference to the following specification and drawings.

1 is a schematic diagram of an acoustic touch screen according to the prior art. 6 is a graph showing signal amplitude with respect to time of a waveform signal received by a surface acoustic wave transducer for one axis of a touch screen according to the prior art. It is a graph which shows the signal amplitude with respect to time of the waveform similar to FIG. 3 when a waveform is disturbed by touching on a touch screen. FIG. 4 is a graph when a waveform propagating across the surface of the touch screen in a direction perpendicular to the waveform shown in FIGS. 2 and 3 is disturbed. 4 is a flowchart illustrating one method according to the present invention. 6 is a flowchart showing another method according to the present invention. FIG. 2 is a schematic diagram illustrating a controller according to the present invention that corrects for overall variation. It is a flowchart explaining the technique used in order to adjust the frequency of the digital multiplier shown in FIG. It is the schematic which shows a quadrature sum detector. It is a flowchart explaining the method of another embodiment shown in FIG. FIG. 2 is a schematic diagram illustrating an adaptable controller according to the present invention that corrects for global and partial variations. FIG. 16 is a schematic diagram illustrating a digital burst processor used in the adaptable controller shown in FIGS. 11 and 15. It is the schematic which shows the controller which can be directly mounted in a touch screen board | substrate. FIG. 16 is a schematic diagram illustrating a method according to another embodiment shown in FIG. 15. FIG. 2 is a schematic diagram illustrating an adaptable controller according to the present invention that frequently compensates for global and partial variations. FIG. 3 is a schematic diagram illustrating an adaptable controller according to the present invention in which only the reception center frequency is adjusted. FIG. 6 is a schematic diagram illustrating an acoustic touch screen using a set of additional transducers for touch screen characteristics.

  FIG. 1 is a diagram illustrating a touch screen 100 using surface acoustic waves according to the prior art. This type of touch screen is preferably utilized with a cathode ray tube (or CRT) display, a liquid crystal display (or LCD), or other type of display. A common type of acoustic touch screen employs Rayleigh waves. In this specification, the term Rayleigh wave is used to include a quasi-Rayleigh wave, U.S. Pat.Nos. 4,642,423, 4,645,870, 4,700,176, granted to Adler et al. 4,746,914, 4,791,416, and reissued patent 33,151; 4,825,212 granted to Brenner et al. And U.S. Pat. Nos. 5,708,461 and 5,854,450 to Kent. Acoustic touch screens are also known that employ other types of sound waves, such as Lamb waves and transverse waves, or a combination of other types of sound waves (including Rayleigh waves). Such acoustic touch screens are described in U.S. Pat.Nos. 5,591,945 and 5,854,450 to Kent, U.S. Pat.Nos. 5,072,427, 5,162,618, 5,177,327, 5,243,148, 5,329,070 to Knowles, No. 5,573,077 and in US Pat. No. 5,260,521 to Knowles. The documents cited herein are hereby incorporated in their entirety for all purposes. A brief description of a surface acoustic wave touch screen will now be provided to assist in a more detailed understanding of the present invention.

  The touch screen 100 has a substrate 101 suitable for propagating surface acoustic waves, such as Rayleigh waves, Love waves, and other waves that are sensitive to touch on the surface. The system has a transmit transducer 105, a receive transducer 107, and a pair of associated reflective arrays 109, 111 and determines a touch coordinate axis along the x-axis 103. A similar system has a transmit transducer 115, a receive transducer 117, and associated reflective arrays 119, 121, and determines a coordinate axis along the y-axis 113. Transmit transducers 105 and 115 are typically connected to a controller 123 that is controlled by a processor 125. Similarly, the receiving transducers 107 and 117 are connected to a controller 123 that includes a signal processing system 127. Signals may be supplied to the transducers 105 and 115 simultaneously, but it is preferable to supply the signals sequentially to reduce the interface and crosstalk between the two coordinate sensing channels. According to the method of sequentially detecting signals, many necessary circuits can be used alternately, so that it is possible to eliminate the necessity of providing duplicate circuits and reduce the complexity of the circuits. . Also, to further reduce circuit complexity, both transmit transducers 105, 115 typically transmit bursts having the same frequency.

  Hereinafter, one detection channel will be described in detail. The following channel description applies equally to the second sensing channel. To determine the touch coordinates along the x-axis 103 on the substrate 101, the transmit transducer 105 emits a burst sound wave (eg, a burst sound wave of about 5 microseconds) along the path 129. Since the burst sound wave has a relatively wide bandwidth, the frequency is not so clearly limited. The reflective array 109 includes a plurality of reflective elements 131 disposed along the path 129, and each reflective element is disposed so as to be inclined at an angle of about 45 degrees with respect to the path 129. Each reflecting element 131 extracts a plurality of wave components 133 from the sound wave propagating along the path 129, and the wave components 133 preferably propagate along the surface of the substrate 101 along the y-axis 113. Designed. The pattern of the reflective array 109 is designed to generate a linear wavefront having a substantially uniform amplitude by coherently adding the individual wave components reflected by the individual reflective elements 131. These wave components 133 are recombined by a plurality of reflective elements 135 in the reflective array 111, and each reflective element 135 directs the wave components along the path 137 to the receiving transducer 107. The individual reflective elements 135 of the array are arranged along a path 137 and are arranged at a point that is inclined at an angle of about 45 degrees with respect to the path. The receiving transducer 107 is a relatively long-term signal (eg, about 150 microseconds) rather than a short burst due to the time delay that the sound waves emitted from the transmitting transducer 105 change due to the speed of sound associated with the substrate 101. Receive.

The receiving transducer 107 converts a wave signal received along the path 137 into an electrical signal. This electrical signal is analyzed for the arrival time of the received wave, for example. FIG. 2 is a graph showing a typical time analysis of such a wave. The amplitude of the received wave over time, ie the envelope of the RF (radio frequency) signal is shown. At time t ₁ , a signal is provided from the signal source 123 to the transducer 105. At time t ₂ , a wave signal is first received by the transducer 107. The delay time between times t ₁ and t ₂ is that the wave is emitted from transducer 105, arrives at the first reflective element 139 of array 109, propagates across the surface of panel 101, and the first reflection of array 11. This corresponds to the delay time until reflection by the element. At time t ₃ , the last wave reaches the transducer 107. Depending on the spacing and design of the reflective elements of the array, the envelope amplitude from time t ₂ to time t ₃ is relatively constant if the wave is not blocked.

FIG. 3 is a second graph of the waveform received by the transducer 107. At time t _t , the amplitude of the waveform is shown having a recess 301. The depression 301 is due to attenuation of sound waves at a certain position 143 on the substrate 101. The signal processor 127 can calculate the x-coordinate of the touch 143 by analyzing the delay time from t ₁ to t _{t in} cooperation with the processor 125. Similarly, the processors 125, 127 can work with the signal source 123, the transducers 115, 117, and the reflective arrays 119, 121 to calculate the y-axis of the touch 143. FIG. 4 is a graph of the waveform received by the transducer 117, showing the attenuation dip 401 due to the touch 143.

  FIG. 5 and FIG. 6 are flowcharts showing a basic processing procedure related to the adaptable controller of the present invention. The method shown in FIG. 5 may be performed on the user side (where the user is used), but is most preferably performed during the manufacturing process of the touch screen system. In step 501, one or more characteristic frequencies of a particular touch screen are determined using any of a variety of known test techniques. For example, when tested at the manufacturing site, the touch screen is placed in an inspection jig and formed such that sound waves traverse the surface of the substrate. After one or more characteristic frequencies of the touch screen are determined, the frequency of the controller that is to be used with the touch screen is adjusted to accommodate the measured touch screen frequency (step 503). In general, the frequency of the controller is adjusted until the desired frequency is obtained. Alternatively, the controller may have a look-up table that records a controller setting value according to the obtained output frequency. Preferably, the look-up table is specific to the individual controller, i.e. each controller has a look-up table that depends on its own variation. After the operating frequency of a particular touch screen is determined, the controller is properly set up using a look-up table for the controller coupled to that touch screen. Regardless of how the controller is adjusted, once the controller is applied to the substrate, the touch screen system can be assembled (step 505).

  According to the method shown in FIG. 6, the controller and the touch screen are coupled before attempting to adapt the two frequencies of the controller and the touch screen (step 601). Thereafter, installation as a touch screen system is completed (step 603), and initialization of the system is started (step 605). During system initialization, the touch screen is tested to determine one or more characteristic frequencies (step 607). Preferably, the test process uses a touch screen standard transmit / receive transducer (such as 105/107 and / or 115/117) operating in a single burst test mode. Alternatively, a pair of dedicated transducers may be used. Once one or more characteristic frequencies of the substrate are determined, the controller frequency is adjusted (step 609) to prepare the system for normal operation (step 611).

  In the variant shown in FIG. 6 of the method described above, optimal frequency adaptation can be ensured by designing the system to periodically adjust the controller during touch operations. However, in contrast to the system described above, a periodic test sequence of retesting the touch screen and recalibrating the controller is performed (step 613). The controller may be readjusted every time the system enters the start-up sequence or every time a predetermined period has elapsed. In general, it is preferable to periodically adjust the controller if the touch screen substrate or controller is subject to fluctuations due to temperature. When a polymer substrate is used, the speed of sound waves on the substrate is likely to vary with changes in ambient temperature. Similarly, if the controller does not use a crystal oscillator, the reference frequency is likely to drift (fluctuate), so the controller needs to be adapted frequently.

  If the touch screen system fails on the user side due to touch screen substrate failure or controller failure due to vandalism etc., the above described adaptive controller has obvious advantages. The controller frequency can be adapted so that a new touch screen or a new controller can be easily installed on site. This is preferred compared to sending an adapted touch screen / controller to the user side for the manufacturer to return the entire touch screen system for repair or to replace in the field. For example, when the touch screen of an existing touch screen system needs to be replaced, the old controller performs a new initialization test to identify one or more characteristic frequencies of the new touch screen and adjust the controller frequency. It can be reset to adapt to the new characteristic frequency. Alternatively, a new touch screen identification code can be used to set the controller frequency with reference to the lookup table described above. Similarly, if a new controller is needed on the user side, the new controller can be adapted to the existing touch screen by initialization tests, or set with reference to the lookup table and the old touch screen identification code. May be. According to the latter method, the controller can be set at either the manufacturer's factory or the user side.

  The present invention has a number of embodiments, each providing the ability to adapt the controller frequency to the touch screen conditions (frequency). In these embodiments, the cause of the frequency mismatch that the adaptable controller adjusts is different. The embodiment shown in FIG. 7 is used in a system that addresses “overall” frequency non-adaptive errors, ie, errors that globally affect frequency adaptability between the controller and the touch screen. . For example, the speed of sound waves in a piece of glass usually varies exactly with its composition. That is, when the glass composition varies between glass production lots or between glass suppliers, the speed of sound waves varies between glass production lots, even if the factors affecting the frequency are well controlled. Therefore, the overall frequency characteristics of the touch screen are affected by an error caused by the variation in composition. According to certain embodiments, glass tempering steps are often required in touch screen manufacturing processes, but the characteristic frequency varies between individual touch screens depending on the time and temperature characteristics of the glass tempering step. There is a case.

  In touch screens having an overall frequency non-adaptive error (due to glass composition variations), the adaptive controller according to the present invention preferably uses a single adaptive frequency algorithm. In this case, if the non-adaptation between the controller and the touch screen does not change with time, it is not necessary to adapt the frequency multiple times or continuously. Rather, this embodiment contemplates a randomly selected touch screen and a randomly selected controller (ie, an unpaired touch screen and controller pair) in the final system assembly. To ensure a successful pairing during a system recovery or system recovery. Therefore, this applied frequency algorithm is preferably executed during the initial activation sequence of the paired touch screen and controller.

  The embodiment of the adaptable controller shown in FIG. 7 employs analog signal processing techniques. However, it should be understood that digital signal processing can be employed in this embodiment as well. In the controller 700, a crystal oscillator 701 that vibrates at a frequency close to a desired frequency is provided. An output from the reference oscillator 701 is supplied to a microprocessor 705 and a digital multiplier 703 (also referred to as a digital divider) in the controller 700. The digital multiplier 703 mathematically changes the output from the crystal oscillator (eg, by multiplying the frequency of the crystal oscillator by a rational number A / B) based on a command sent from the microprocessor 705 to the digital multiplier 703; Generate the desired frequency. That is, the digital multiplier 703 cooperating with the crystal oscillator 701 constitutes a main oscillator 704 for analog components associated with the touch screen.

  A tone burst is generated using the output signal from the digital multiplier 703, and the tone burst is output along the analog line 707 to the touch screen transmit transducer (eg, transducers 105, 115 of FIG. 1). The tone burst has a frequency output by the multiplier 703 and has a burst length determined by a burst circuit 709 connected to the microprocessor 705. Tone bursts are typically conditioned and amplified by a burst amplifier 711 before being transmitted to a transmit transducer.

  In order to determine the desired operating frequency, the output signal from the receiving transducer (107, 117 in FIG. 1) is sent via line 713 to the mixer built-in circuit 715. Preferably, the output signal from the transducer first passes through a bandpass filter 717 and an RF amplifier 719. Usually, the band input filter 717, which is a fixed broadband filter, is mainly used as a noise suppression circuit to adjust the RF input signal. The RF amplifier 719 amplifies the signal to a desired level. The mixer built-in circuit 715 compares the frequency component of the adjusted and amplified signal from the receiving transducer with the output signal from the digital multiplier 703, and outputs a substantial DC baseband signal that varies considerably slowly. . An output signal from the mixer built-in circuit 715 is digitized by the AD converter 723 and supplied to the microprocessor 705. Although optional, the low-pass filter 721 additionally adjusts the output signal of the mixer built-in circuit before digitization, but the mixer built-in circuit usually performs limited narrowband filtering.

  As mentioned above, component 703 is preferably an A / B digital multiplier. However, comprehensively, component 703 is simply a frequency change circuit, and any digital electronic circuit, analog electronic circuit, or mixed digital / analog electronic that changes the crystal oscillation frequency in response to a control signal from microprocessor 705. It may be a circuit.

  Depending on the application, it may be sufficient to adapt the burst center frequency or the reception center frequency. If it is sufficient to adapt the burst center frequency, the circuit 715 does not require an input signal from the digital multiplier 703. Thus, a more standard detector commonly found in this controller may be substituted. When it is sufficient to adapt the reception center frequency, there is no need to connect between the digital multiplier 703 and the burst circuit 709.

  FIG. 8 is a flowchart illustrating a technique used to adjust the frequency of the digital multiplier 703 to adapt the frequency of the touch screen connected to it. As described above, this embodiment adapts the controller frequency to the touch screen frequency at startup (step 801). Alternatively, the system may be designed to perform frequency adaptation of the controller periodically or only during the first start-up cycle.

  After the activation step 801, the microprocessor 705 sweeps the output signal of the digital multiplier 703 through a predetermined frequency range (step 803). Preferably, the controller first performs a rough (coarse) adjustment process, and then performs a fine (fine) adjustment process. However, these two adjustment processes may be combined to perform a single scanning sequence. it can. Therefore, in step 803, the predetermined frequency range is scanned using a relatively large frequency step. The output signal of the AD converter 723 for each frequency step is collected (step 805) and the maximum signal amplitude indicative of the closest adaptation between the master oscillator output signal and the touch screen is selected (step 806). Next, this scanning / optimization process is repeated by scanning the output frequency of the master oscillator near the previously selected frequency using smaller frequency steps (steps 807-809). The frequency determined in step 809 as closest to the characteristic frequency of the touch screen is input to the memory (step 811), and the frequency of the output signal of the main oscillator circuit can be reliably maintained at a desired frequency.

  Although FIG. 8 illustrates a two-stage frequency scanning method, those skilled in the art will appreciate that there are many other techniques for determining the desired output frequency. The present invention can also employ a dither method or a successive approximation method, for example.

  The basic algorithm of FIG. 8 does not require the use of an AD converter sum. In general, steps 805 and 808 represent collecting any measurable amount that suggests the degree of frequency maladaptation, and steps 806 and 809 select a measurable amount corresponding to a small frequency maladaptation within an acceptable range. Represents what to do. For example, the microprocessor 705 may count the number of RF cycles of both the received signal and the output signal of the digital multiplier 703 in a predetermined time interval. Frequency mismatch can be measured by the difference in the number of RF cycles. Other circuits and techniques that accomplish the same purpose are well known to those skilled in the art.

  FIG. 9 shows a quadrature-sum detector as an illustrative example of the mixer built-in circuit 715. The adjusted RF input signal 901 is mixed with the oscillator output from the digital multiplier 703 of the mixer 903. The mixer 903 outputs a sum frequency and a difference frequency of two input frequencies. The sum frequency is about 10 MHz and is removed using a low pass filter 905. The remaining frequency is close to 0, ie, baseband. The single mixer circuit described above is used to output a baseband signal, which depends on the relative phase of the oscillator output and the RF input signal. In order to achieve relative phase independence, that is, to avoid the beat pattern of the waveform digitized by the AD converter 723, the quadrature sum detector has two channels as shown in FIG. As shown in the figure, the phase of the frequency input from the oscillator is shifted by 90 degrees using the second mixer 907. The output signal of the second mixer 907 passes through another low-pass filter 905 and then summed with the output signal from the first channel in the quadrature sum circuit 909. The output signal of circuit 909 is a baseband signal 911 without a beat pattern and is independent of the exact phase of the received signal. In effect, the quadrature sum detector of FIG. 9 provides a narrowband bandpass filter whose center frequency is adjustable and controlled by the frequency of the output of the digital multiplier 703.

  The mixers 903 and 907 shown in FIG. 9 are essential components of the quadrature sum detector as well as other available components of the built-in mixer circuit. Mixer 903 combines, for example, the signal from line 713 and the output signal of source 704 to obtain a desired output that is a function of the two input signals and is a function of the difference between their frequencies. The entire quadrature sum detector may not be required. For example, if only the burst frequency needs to be adjusted, the required output signal value is the difference beat between the signal from line 713 and the signal from source 704. Such a difference frequency signal can be easily generated by a diode mixer. Of course, other mixer devices are known to those skilled in the art and can be utilized in variations of the present invention.

  In another embodiment of the present invention shown in FIGS. 10-12, the controller may determine the overall variation, ie, the frequency variation that has a certain effect on the characteristic frequency of the entire touch screen, and the partial variation, ie, the portion of the touch screen. Can be programmed to accommodate both frequency variations within a typical region. For exemplary purposes, this embodiment uses digital signal processing techniques. However, it should be understood that this embodiment can be implemented using analog signal processing techniques as well.

  FIG. 10 is a flowchart for explaining a procedure related to this embodiment. After the manufacture of the touch screen substrate including the required array deposition step and glass tempering step is completed, the characteristic frequency of the touch screen, including the effects of partial deformation of the array, is measured (step 1001). Preferably, these measurements are made in a manufacturing plant using a manufacturing floor test facility. Based on these measurements, a series of frequency correction values are typically calculated as a function of delay time for both x-axis and y-axis coordinates (step 1003). Thereafter, a set of correction values specific to an individual touch screen is then loaded into the memory of the adaptive controller 1100 (step 1005), which is then coupled to this particular touch screen (step 1007). It is understood that steps 1005 and 1007 may be reversed in order, and the measurement step 1001 of the frequency variation of the touch screen substrate may be combined with the correction value calculation step 1003.

  According to a modification in which the method shown in FIG. 10 is slightly changed, an identification code is given to each touch screen substrate. Preferably, a table relating to identification codes and unique correction values associated with each identification code is recorded by the manufacturer, the seller or both. That is, for example, when it becomes necessary to replace the controller due to damage or the like, the user only has to notify the identification code in order to obtain a new controller in which necessary correction values are read in advance.

  In the embodiment of FIGS. 11 and 12 according to the present invention, the adaptable controller 1100 utilizes an oscillator 1101 as a reference. It is preferable to use a stable crystal oscillator as the frequency source. The output signal from the oscillator 1101 is sent to a frequency divider / phase shifter. The divider / phase shifter divides the frequency from a frequency of about 22 Mhz to a desired frequency of about 5.53 MHz, and shifts (phase shifts) the phase of a portion of the output signal by 90 degrees. The oscillation frequency 1105 that is not phase-shifted and the oscillation frequency 1107 that is phase-shifted are appropriately filtered in the mixers 1109 and 1111 and mixed with the amplified RF signal of the receiving transducer. As with the controller 700, the RF signal from the touch screen receiving transducer is typically filtered with a bandpass filter 1113, which is a fixed wideband filter, to remove various noise components and achieve the desired signal level. Therefore, it is amplified by the amplifier 1115.

  The output signals of the mixers 1109 and 1111 represent the amplitudes of the x and y signals in the complex plane. That is, by using a pair of mixers and a pair of reference signals, one of which is phase-shifted by 90 degrees, it is possible to specify the phase and the amplitude of the complex display independent of the phase. The output signals of the mixers 1109 and 1111 pass through a pair of low-pass filters 1117 and 1119, respectively, and are digitized by AD converters 1121 and 1123, respectively. These signals are then sent to a digital signal processor (ie, DSP) 1125.

  The DSP 1125 functions as a frequency filter that can mathematically control both the center frequency and the bandwidth. Methods for mathematically controlling the DSP 1125 to obtain controllable bandwidth and center frequency are well known to those skilled in the art and will not be described in detail here. A memory 1127 is connected to the DSP 1125. The memory 1127 stores correction values obtained by measuring frequency characteristics of a specific touch screen (ie, a touch screen coupled with the controller 1100). The DSP 1125 responds to a specific center frequency based on the correction value stored in the memory 1127. Preferably, the DSP 1125 is responsive to a center frequency that varies in response to the delayed signal and takes into account variations due to partial variations in the acoustic reflection array.

  Item 1125 in FIG. 11 is a digital signal processor (ie, DSP) in the general term meaning. Digital signal processing means mathematical or digital processing of digital signals from the AD converters 1121 and 1123. The DSP 1125 can be implemented in a number of ways. For example, the DSP 1125 may be program code executed by the microprocessor 1131. Alternatively, the DSP 1125 may be a digital circuit custom designed for a sonic touch screen controller. Furthermore, digital signal processing may be performed on, but not limited to, a packaged silicon chip called a “DSP chip” often quoted by electronic engineers.

  An output signal from the crystal oscillator 1101 is supplied to the digital burst circuit 1129 to emit a transmission transducer burst. Burst circuit 1129 processes this output signal in accordance with the instructions received from microprocessor 1131 and then receives instructions regarding the desired center frequency from permanent memory 1127. If necessary, the output of the digital burst circuit 1129 is amplified by a burst amplifier 1133 before being transmitted to the transmit transducer via line 1135.

  FIG. 12 is a schematic diagram showing a specific example of the digital burst circuit 1129. The burst circuit 1129 includes a bit register 1201 (for example, a 64 × 8 bit register) connected to the microprocessor 1131. The microprocessor 1131 loads a desired bit pattern (that is, a digital pattern generated by the microprocessor 1131 in response to the output signal of the permanent memory 1127) into the register 1201. The bit pattern determines the burst center frequency. For each burst, the bit pattern loaded into register 1201 is latched into shift register 1203 that is clocked out to generate the burst. As will be appreciated, variations between the two axes can be taken into account by using different bit patterns to determine the burst center frequency for the x and y coordinates of the touch screen. It should be noted that the bit pattern may be calculated in response to frequency correction data from the memory 1127, or calculated by the microprocessor 1131 or recorded directly in the memory 1127.

  In another example where an adaptable controller according to this embodiment can be utilized, the touch screen uses a grating transducer. In the diffraction grating transducer, the piezoelectric element is disposed on the rear surface of the substrate, and the diffraction grating is disposed on the front surface of the substrate. The diffraction wave is used to coherently diffract the pressure wave generated by the piezoelectric element to generate a sound wave that propagates along the surface of the substrate. Such grating transducers have been found to be most efficient when the operating frequency matches the glass thickness resonance frequency. Since the glass thickness resonance frequency of the substrate depends on the thickness of the substrate, it is preferable to first measure the glass thickness, then calculate the optimum operating frequency, and find the appropriate reflective array and diffraction grating for that optimum operating frequency. Designed. The controller frequency is adapted to the characteristic frequency of the touch screen using an adaptable controller according to the present invention, for example, the controller 1100. However, unlike some applications of this embodiment, this specific example requires the adaptable controller to have a function to vary the burst frequency by about 10-20% from the frequency of the reference oscillator. Any receive band filter, such as filter 1113, needs to be tunable or sufficiently wide band to fully cover the variation range of the characteristic frequency of the touch screen.

  FIG. 13 is a schematic diagram illustrating another embodiment of an applicable controller, which is advantageous in both size and cost because it is mounted directly on a touch screen substrate. In this embodiment, since the crystal oscillator is replaced with the local oscillator 1301, a desired size can be obtained. The local oscillator 1301 may be composed only of circuit components on a silicon chip, for example. If there is a drift in the local oscillator 1301 relative to the crystal oscillator, a feedback loop is required to achieve the required frequency stability. With the feedback loop, the controller 1300 actively or repeatedly adapts the oscillation frequency to the desired frequency.

  Similar to the embodiment described above, the RF signal from the touch screen receive transducer is first conditioned by passing through a bandpass filter 1303 and an amplifier 1305. The adjusted RF signal is mixed with the output signal of local oscillator 1301 in mixer 1307. The oscillator 1301 is a variable frequency oscillator whose frequency is controlled by an input voltage, for example. Using a suitable buffer circuit between the capacitor 1308 and the oscillator 1301, the oscillator 1301 can provide other types of electrical input signals such as current. In this embodiment, the local oscillator or reference oscillator operates at a frequency greater than the frequency of the touch screen. For example, for a nominal touch screen frequency of 5.5 MHz, the oscillator 1301 may operate at a frequency of about 6 MHz. Thereafter, the output signal from the mixer 1307 is set to an intermediate frequency of about 500 kHz.

  The intermediate frequency signal output from the mixer 1307 passes through the band filter 1309 before being input to the discriminator 1311. The discriminator 1311 has a sign that depends on whether the frequency of the intermediate frequency signal is higher or lower than the center frequency of the discriminator 1311 and generates a voltage having an amplitude that depends on the degree of difference from the center frequency of the discriminator. . The frequency of the local oscillator 1301 is adjusted by the varactor diode using the output signal from the discriminator 1311 to reduce the voltage of the output signal of the discriminator to near zero. A switch 1313 connected to the control processor 1314 is part of the sample and hold circuit, which allows the local oscillator 1301 to be held at the previously specified frequency between burst / receive cycles. Switch 1313 is closed during the receive cycle.

  During system startup, the local oscillator 1301 may deviate from the desired frequency with a substantial margin and prevent the feedback loop from effectively stabilizing the oscillator. In this case, the controller 1300 preferably has a ramp function that gradually adjusts the frequency of the local oscillator 1301 until the feedback loop functions. In one operating mode, during startup, switch 1313 is open and second switch 1315 is closed. A digital-to-analog converter (ie, DAC) 1317 adjusts the frequency of the oscillator 1301 under the control of the microprocessor 1314 and increases (or decreases) the frequency while watching the output signal of the mixer 1307 with the detector 1319. . The detector 1319 is connected to the microprocessor 1314 via the AD converter 1321. When the output signal of detector 1319 exceeds a predetermined threshold, indicating that local oscillator 1301 approximates the desired frequency, microprocessor 1314 allows the feedback loop to fine tune the local oscillation frequency. Then, the switch 1315 is opened and the switch 1313 is closed. Alternatively, both switches 1313 and 1315 may be closed during startup. In this mode, when the oscillation frequency falls within the band of the bandpass filter 1303, the microprocessor 1314 opens the switch 1315 so that the feedback loop can fine tune the frequency from this point onwards.

  In contrast to the embodiment described above, the frequency of the local oscillator 1301 is not adjusted to the desired burst frequency. Rather, the frequency of the local oscillator 1301 follows the frequency of the touch screen and is maintained so that the difference between the frequency of the local oscillator and the frequency of the touch screen is constant (in this example, 500 kHz). Thus, to achieve the desired burst frequency, the stabilized output signal from local oscillator 1301 is mixed with the output signal from intermediate frequency oscillator 1325 in second mixer 1323. The intermediate frequency oscillator 1325 operates at the same frequency as the intermediate frequency band filter 1309 (about 500 kHz in this example). The output signal from mixer 1323 has a desired burst frequency (about 5.5 MHz in this example). A band-pass filter (not shown) is inserted between the mixer 1323 and the burst circuit 1327 and passes only a desired sum frequency or difference frequency from the mixer 1323. Similar to the embodiment described above, the length of the tone burst at this frequency is controlled by a burst circuit 1327 connected to the microprocessor 1314. Typically, the tone burst is amplified to the desired amplitude by a burst amplifier 1329 before being output along line 1331 to one of the touch screen transmit transducers.

  The circuit in FIG. 13 is a specific example of a circuit that shifts the RF frequency of the received signal by a lower frequency, but the frequency to be shifted is not necessarily a baseband such as about 500 kHz. This is a technique widely used by designers of adaptive frequency controllers. The lower frequency selection can be anywhere between the RF frequency and the baseband. The optimum value depends on the details of the particular circuit, noise source, etc.

  FIGS. 14-15 illustrate another embodiment of the present invention that is most suitable for touch screens where the speed of sound waves on the substrate varies during use. For example, as described above, the velocity characteristics of sound waves on a polymer substrate may depend on temperature. Thus, a touch screen with a polymer substrate will cause a total variation (due to a change in the overall room temperature, for example) or a partial variation (due to different temperatures at different parts of the screen) during use. There is a case. The embodiment shown in FIGS. 14 and 15 is designed to accommodate these variations.

  FIG. 14 is a flowchart illustrating the method of the embodiment, where the controller 1500 is connected to a touch screen that needs to be adapted frequently. In this embodiment, the first step is to determine whether or not the touch screen has detected a touch (contact) (step 1401). When the touch is not detected, the controller 1500 executes a test sequence (test routine) for determining the frequency characteristic of the touch screen. Preferably, the first step is to determine the time that has elapsed since the last execution of the test routine (step 1403). If the preset time has not elapsed (step 1405), the system loop returns to the starting point. If the preset time has elapsed, the system measures the frequency characteristics of the substrate with respect to the x and y coordinates of the substrate (step 1407) and determines a set of correction values (step 1409). These correction values are recorded in the memory of the controller (step 1411), and the system loop returns to the starting point (step 1413). When a touch is detected (step 1415), the system identifies touch coordinates (step 1417) and sends these coordinates to the motion system (step 1419).

  A frequently adaptable controller 1500 is shown in FIG. This controller is basically the same as the controller 1100 except for some changes. For example, the permanent memory 1127 is replaced with a temporary memory 1501. Similar to the controller 1100, the memory 1501 stores a frequency correction value necessary for correcting fluctuations in the characteristic frequency of the touch screen. The temporary memory according to this embodiment is necessary when the controller 1500 periodically updates the correction value as described above. Furthermore, since the memory needs to be updated periodically, it communicates bidirectionally to the microprocessor 1131. Therefore, during the characteristic test sequence, the microprocessor 1131 determines a desired frequency correction value using the output signal of the DSP 1125 and stores it in the memory 1501.

  In the embodiment shown in FIG. 11, the digital burst processor 1129 outputs a burst signal having a desired burst frequency. Further, the power spectrum of the output burst signal is adjusted based on the correction value stored in the temporary memory 1501. Time modulation of the phase of individual RF pulses (eg, pulse phase based on sin (x) / x curve), amplitude modulation of burst train (eg, trapezoidal envelope or stack of a series of digital pulses of different lengths), or Various techniques can be used to adjust the burst power spectrum, including using non-integrated burst lengths in units of the RF cycle.

  According to the embodiment shown in FIG. 16, only the center frequency of the received signal to be processed is adjusted, and the frequency of the burst signal is not adjusted. This embodiment adjusts the frequency of the burst signal when the burst is very short, for example, has a duration of less than 10 cycles of the RF signal and is wide enough to cover the expected variation in the characteristic frequency of the touch screen It can be applied when it is not necessary to do so.

  As shown in FIG. 16, the microprocessor 1601 receives a nominal RF operating frequency and activates a burst circuit 1603 that executes a transmit transducer (not shown). Similar to the above-described embodiment, the output signal of the burst circuit 1603 can be adjusted using the burst amplifier 1605. The narrow band filter in the receiving circuit chain is a variable band filter 1607. The center frequency of the variable band filter 1607 is controlled by the voltage provided by the DA converter 1609, and the DA converter 1609 is controlled by the microprocessor 1601. Appropriate circuit designs for variable bandpass filters such as filter 1607 are well known by those skilled in the art and will not be further described. A signal from a receiving transducer (not shown) may pass through a relatively wide band filter 1611 and be amplified by an amplifier 1613 before passing through a variable band filter 1607 that determines the center frequency. The signal is converted from an RF signal to a baseband signal by a detector 1615 and digitized by an AD converter 1617. The microprocessor 1601 determines an optimum setting for the DA converter 1609 by using, for example, the processing shown in FIG. The optimal DA converter settings are then stored in the memory 1619 and the microprocessor 1601 uses the stored values during normal touch processing. You may memorize | store the value of a separate DA converter with respect to x signal and y signal.

  In each of the embodiments described above, it is preferable to adapt the controller to the touch screen using transducers used for touch detection, such as transducers 105, 107, 115 and 117. That is, for example, a received signal generated from a sound wave emitted from the transducer 105 and received by the transducer 107 is used as a reference frequency of an adaptable controller according to the present invention, or touched by the same or similar method as a conventional touch screen. It can be used to provide information. However, the transducer used to determine the characteristic frequency of the touch screen and adapt the controller need not be the same as the transducer used for touch sensing and information gathering. For example, as shown in FIG. 17, a pair of transducers 1701, 1703 are used in a delay line feedback oscillator (not shown) to determine the characteristic frequency of the touch screen, but the transducer 105, used in touch sensing, 107, 115, 117 can be added. Alternatively, a separate transducer with a separate reflective array may be provided on the back side of the touch screen substrate. Preferably, the input and output signals of the added transducer are multiplexed on line 707, 713 of controller 700 or the corresponding line of controller 1100, 1300 or 1500. This method provides a degree of freedom to optimize the characteristics of the frequency reference signal, independent of the need for touch sensitive sound wave paths.

  While several embodiments of the present invention have been described and illustrated above, it should be understood that other embodiments using the adaptation method according to the present invention are possible. In addition, it should be understood that various aspects of the above-described embodiments can be modified without departing from the invention. For example, the non-crystal reference oscillator and feedback loop used in the embodiment shown in FIG. 13 may be used in place of the crystal oscillator used in the embodiment shown in FIGS. That is, the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. Accordingly, the disclosure and description herein are intended to be illustrative, not limiting, of the scope of the present invention as set forth in the claims.

DESCRIPTION OF SYMBOLS 100 Touch screen 101 Board | substrate 105,115 Transmission transducer 107,117 Reception transducer 109,111 Reflection array 123 Controller 125 Processor 127 Signal processor 1701,1703 Transducer

Claims (18)

A substrate through which sound waves can propagate;
At least one transmission transducer connected to the substrate for transmitting acoustic waves of a first burst length in response to an input signal;
A reflection array having a plurality of sound wave reflection parts connected to a substrate, wherein the sound wave of a first burst length is lengthened to form a sound wave of a second burst length;
At least one receiving transducer connected to the substrate for receiving a second burst length of sound waves;
An adaptable controller connected to at least one transmitting transducer and at least one receiving transducer;
Applicable controllers are
A reference oscillator for generating a first frequency;
A microprocessor connected to a reference oscillator;
A digital burst circuit connected to a microprocessor, a reference oscillator, at least one transmission transducer, and outputting an input signal to the at least one transmission transducer in response to a burst control signal;
A memory including a set of frequency correction values connected to a microprocessor;
A touch screen system, wherein the microprocessor outputs a burst control signal to a digital burst circuit.   The touch screen system according to claim 1, wherein the reference oscillator is a crystal oscillator.   The touch screen system of claim 1, wherein the burst control signal is a bit pattern.   The touch screen system of claim 1, wherein the set of frequency correction values is transmitted to the memory by a microprocessor.   The touch screen system of claim 1, further comprising a frequency divider connected to a reference oscillator.   The touch screen system of claim 1, wherein the at least one transmission transducer is a diffraction grating transducer. A method for controlling a touch screen system, comprising:
A storage step of storing a set of frequency correction values in a memory;
A first transmission step of transmitting a set of frequency correction values to the digital signal processor;
Receiving a first waveform signal with a receiving transducer;
And calculating a second waveform signal from the first waveform signal and the set of frequency correction values using a digital signal processor. A first generation step of generating a set of frequency correction values using a microprocessor;
The method according to claim 7, further comprising a second transmission step of transmitting a set of frequency correction values to the memory. An analysis step for periodically analyzing the first waveform signal received by the receiving transducer;
A second generating step for generating a set of frequency correction values in response to the analysis;
The method according to claim 7, further comprising a second transmission step of transmitting a set of frequency correction values to the memory. A method for controlling a touch screen system including a touch screen having a characteristic frequency, comprising:
Generating a signal having an adjustable first frequency;
Mixing the output signal from the receiving transducer with a signal having a first frequency to produce a signal having a second frequency;
A filtering step of passing a signal having the second frequency through a bandpass filter;
A comparing step of comparing the second frequency of the filtered signal with the characteristic frequency of the touch screen;
Adjusting the first frequency until the filtered second frequency is substantially equal to the desired frequency. A setting step of setting the first frequency to an initial frequency at the time of system startup;
A ramp step for ramping the first frequency from the initial frequency through a range of frequencies and an abort step for aborting the ramp step when the filtered second frequency is within a predetermined difference from the desired frequency; The method of claim 10, comprising: Mixing a first frequency signal with an output signal of the intermediate frequency oscillator to produce a signal having a third frequency;
A first transmission step of transmitting a signal having a third frequency to the burst circuit;
A generating step for generating a burst signal;
11. The method of claim 10, further comprising a second transmission step of transmitting the burst signal to a transmission transducer connected to the touch screen system. A method of operating a touch screen system,
Providing a plurality of characteristic frequencies for a particular touch screen controller;
A measurement step for measuring a set of operating frequency characteristics on a specific touch screen substrate;
Connecting a specific touch screen controller to a specific touch screen substrate; and
Selecting from at least one characteristic frequency that is substantially adapted to the substrate operating frequency from a plurality of characteristic reception frequencies. The method of claim 13 , wherein the plurality of characteristic frequencies is controllable. Associating a plurality of controllable frequency characteristics with a plurality of touch screen controller settings for a particular touch screen controller;
15. The method according to claim 14 , further comprising the step of recording an associated controllable frequency characteristic and a look-up table for controller settings. The method of claim 13 , wherein the selecting step comprises selecting a particular controller setting to achieve a characteristic frequency. The method of claim 13 , wherein the plurality of characteristic frequencies is a plurality of partial reception characteristic frequencies. The method of claim 17 , wherein the selecting step selects a set of partial reception characteristic frequencies from a plurality of partial reception characteristic frequencies.

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